J/AJ/158/16 Identification of RR Lyrae stars from the DES (Stringer+, 2019)
Identification of RR Lyrae stars in multiband, sparsely sampled data from
the Dark Energy Survey using template fitting and random forest classification.
Stringer K.M., Long J.P., Macri L.M., Marshall J.L., Drlica-Wagner A.,
Martinez-Vazquez C.E., Vivas A.K., Bechtol K., Morganson E.,
Carrasco Kind M., Pace A.B., Walker A.R., Nielsen C., Li T.S., Rykoff E.,
Burke D., Carnero Rosell A., Neilsen E., Ferguson P., Cantu S.A.,
Myron J.L., Strigari L., Farahi A., Paz-Chinchon F., Tucker D., Lin Z.,
Hatt D., Maner J.F., Plybon L., Riley A.H., Nadler E.O., Abbott T.M.C.,
Allam S., Annis J., Bertin E., Brooks D., Buckley-Geer E., Carretero J.,
Cunha C.E., D'Andrea C.B., da Costa L.N., De Vicente J., Desai S., Doel P.,
Eifler T.F., Flaugher B., Frieman J., Garcia-Bellido J., Gaztanaga E.,
Gruen D., Gschwend J., Gutierrez G., Hartley W.G., Hollowood D.L.,
Hoyle B., James D.J., Kuehn K., Kuropatkin N., Melchior P., Miquel R.,
Ogando R.L.C., Plazas A.A., Sanchez E., Santiago B., Scarpine V.,
Schubnell M., Serrano S., Sevilla-Noarbe I., Smith M., Smith R.C.,
Soares-Santos M., Sobreira F., Suchyta E., Swanson M.E.C., Tarle G.,
Thomas D., Vikram V., Yanny B.
<Astron. J., 158, 16 (2019)>
=2019AJ....158...16S 2019AJ....158...16S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry, ugriz ; Cross identifications
Keywords: catalogs - galaxy: halo - galaxy: structure - methods: statistical -
stars: variables: RR Lyrae
Abstract:
Many studies have shown that RR Lyrae variable stars (RRL) are powerful
stellar tracers of Galactic halo structure and satellite galaxies. The
Dark Energy Survey (DES), with its deep and wide coverage (g∼23.5 mag in
a single exposure; over 5000 deg2) provides a rich opportunity to search
for substructures out to the edge of the Milky Way halo. However, the
sparse and unevenly sampled multiband light curves from the DES wide-field
survey (a median of four observations in each of grizY over the first
three years) pose a challenge for traditional techniques used to detect
RRL. We present an empirically motivated and computationally efficient
template-fitting method to identify these variable stars using three years
of DES data. When tested on DES light curves of previously classified
objects in SDSS stripe 82, our algorithm recovers 89% of RRL periods
to within 1% of their true value with 85% purity and 76% completeness.
Using this method, we identify 5783 RRL candidates, ∼28% of which are
previously undiscovered. This method will be useful for identifying RRL
in other sparse multiband data sets.
Description:
DES is a five-year multiband (grizY) imaging survey using the Dark
Energy Camera (Flaugher et al. 2015AJ....150..150F 2015AJ....150..150F) on the 4 m Blanco
Telescope at Cerro Tololo Inter-American Observatory (CTIO). This work
is based on the DES internal Year 3 Quick Release catalog (hereafter
Y3Q2), which contains all the single-epoch data from years 1-3 that
formed the basis for the coadded DES first public data release
(http://des.ncsa.illinois.edu/releases/dr1) (Abbott et al.
2018ApJS..239...18A 2018ApJS..239...18A, hereafter DR1).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 31 8714 *Error rescaling coefficients for Equation (2)
table5.dat 16 100 Estimated RRab selection purity & completeness
table6.dat 96 5782 DES RRab candidates
table11.dat 1465 713816 Full catalog of RRab candidates
lc/* . 14023 DES light curves
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Note on table1.dat: Equation (2) from this paper:
log10(χ2ν,b)=c0,b+c1,b(mb-20)+c2,b(mb-20)2.
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/357 : The Dark Energy Survey (DES): Data Release 1 (Abbott+, 2018)
J/PAZh/27/132 : Parameters of RR Lyrae Type Variables (Dambis+, 2001)
J/AJ/134/973 : SDSS Stripe 82 star catalogs (Ivezic+, 2007)
J/MNRAS/398/1757 : RR Lyraes in SDSS stripe 82 (Watkins+, 2009)
J/ApJ/708/717 : Light curve templates of RR Lyrae stars (Sesar+, 2010)
J/MNRAS/424/2528 : RR Lyrae in SDSS Stripe 82 (Suveges+, 2012)
J/ApJ/763/32 : Galactic halo RRab stars from CSS (Drake+, 2013)
J/ApJ/765/154 : RR Lyrae stars in the Catalina Sky Survey (Drake+, 2013)
J/MNRAS/441/1230 : RRLyr stars in the Catalina Sky Survey (CS2) (Abbas+, 2014)
J/MNRAS/446/2251 : Southern Catalina Survey type-ab RR Lyrae (Torrealba+, 2015)
J/MNRAS/462/4349 : Variable stars in Sculptor dSph (Martinez-Vazquez+, 2016)
J/AcA/67/297 : OGLE Galactic center Cepheids & RR Lyrae (Soszynski+, 2017)
J/AJ/153/204 : RR Lyrae stars from the PS1 3π survey (Sesar+, 2017)
J/ApJ/834/160 : ugriz colors of RR Lyrae in SDSS Stripe 82 (Ngeow+, 2017)
J/ApJ/849/150 : RR Lyrae candidates in the MW outer halo (Cohen+, 2017)
J/MNRAS/469/3688 : CSS Periodic Variable Star Catalogue (Drake+, 2017)
J/AJ/156/241 : A first cat. of variables measured by ATLAS (Heinze+, 2018)
J/ApJ/863/79 : RR Lyrae cand. in Galactic Center (Contreras Ramos+, 2018)
J/A+A/622/A60 : Gaia DR2 misclassified RR Lyrae list (Clementini+, 2019)
http://des.ncsa.illinois.edu/releases/other/y3-rrl : Online Yr 3 RR Lyrae cat.
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- HEALPix [5441/11877] HEALPix region
7 A1 --- Band [grizY] DES filter name
9- 15 F7.4 --- c0 [-0.7953/2.0858]? Error correct coefficient 0
for Band
17- 23 F7.4 --- c1 [-0.6321/0.3225]? Error correct coefficient 1
for Band
25- 31 F7.4 --- c2 [-0.2069/0.0509]? Error correct coefficient 2
for Band
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 F4.2 --- Thrsh [0/0.99] Score threshold
6- 10 F5.3 --- Pur [0/1] Purity (1)
12- 16 F5.3 --- Comp [0/0.983] Completeness (2)
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Note (1): Percentage of objects classified as RRab that were truly so.
Note (2): Percentage of real RRab that were identified as such.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 I14 --- ID DES internal Year 3 Quick Release catalog (Y3Q2)
object ID
16- 25 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
27- 36 F10.6 deg DEdeg Declination in decimal degrees (J2000)
38- 43 F6.3 mag gmagmean [15.213/22.757]? Mean g band (AB) magnitude
45- 50 F6.3 mag rmagmean [15.361/22.733]? Mean r band (AB) magnitude
52- 57 F6.3 mag imagmean [15.373/22.604]? Mean i band (AB) magnitude
59- 64 F6.3 mag zmagmean [15.356/22.77]? Mean z band (AB) magnitude
66- 71 F6.3 mag Ymagmean [15.367/21.587]? Mean Y band (AB) magnitude
73- 78 F6.4 d Per [0.437/0.8227] Period
80- 84 F5.3 mag Amp [0.233/1.556] Best-fit model amplitude
86- 90 F5.2 mag mu [14.71/21.82] Distance modulus µ
92- 96 F5.3 --- p [0.35/0.949] RRab score assigned by the classifier
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table11.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 I14 --- ID DES Y3Q2 ID number
16- 24 I9 --- ID1 DES DR1 ID number (0=not found in DES DR1
coadd catalog, Abbott et al.
2018ApJS..239...18A 2018ApJS..239...18A)
26- 49 F24.20 deg RAdeg Right Ascension in decimal degress
(J2000)
51- 73 E23.20 deg DEdeg Declination in decimal degress (J2000)
75- 96 E22.20 --- p-ab [9.24104e-05/0.949354] Classifier score
for RRab class
98- 119 F22.20 --- EBV [0.000463673/0.585073] Extinction value
from Schlegel et al.
(1998ApJ...500..525S 1998ApJ...500..525S) (1)
121- 140 F20.16 mag gmagmean [-22.3208/24.531]? Mean g (AB) magnitude
measured in light curves (2)
142- 161 F20.16 mag rmagmean [-11.1642/24.7026]? Mean r (AB) magnitude
measured in light curves (2)
163- 182 F20.16 mag imagmean [-11.2687/24.5309]? Mean i (AB) magnitude
measured in light curves (2)
184- 203 F20.16 mag zmagmean [-11.3202/24.5309]? Mean z (AB) magnitude
measured in light curves (2)
205- 224 F20.16 mag Ymagmean [-12.1138/24.5309]? Mean Y (AB) magnitude
measured in light curves (2)
226- 227 I2 --- Nobs-g [0/33] Number of observations in DES g
229- 230 I2 --- Nobs-r [0/37] Number of observations in DES r
232- 233 I2 --- Nobs-i [0/61] Number of observations in DES i
235- 236 I2 --- Nobs-z [0/62] Number of observations in DES z
238- 239 I2 --- Nobs-Y [0/41] Number of observations in DES Y
241- 243 I3 --- Nobs [5/194] Total number of observations
across all bands
245- 263 F19.17 d Per0 [0.434792/0.892838] Period of best
fitting template
265- 283 F19.17 d Per1 [0.434792/0.892838] Period of 2nd best
fitting template
285- 303 F19.17 d Per2 [0.434792/0.892838] Period of 3rd best
fitting template
305- 326 F22.18 --- sigma-DP/P [0.006/0.293]? Uncertainty in
(Pest-Ptrue)/P of the best fit
period
328- 352 F25.20 mag Amp0 [0.000303309/1589.18] Amplitude of best
fitting template (3)
354- 375 E22.20 mag Amp1 [7.22078e-05/817.171] Amplitude of 2nd
best fitting template
377- 398 E22.20 mag Amp2 [3.93605e-05/760.817] Amplitude of 3rd
best fitting template
400- 420 F21.17 mag sigma-Da [-0.012/0.903]? Uncertainty in
(aest-atrue) of the best fit
amplitude
422- 444 F23.18 mag mu0 [-219.091/108.275] Distance modulus of
best fitting template
446- 468 F23.18 mag mu1 [-114.919/56.2675] Distance modulus of
2nd best fitting template
470- 491 F22.17 mag mu2 [-194.008/54.6556] Distance modulus of
3rd best fitting template
493- 514 E22.20 --- Phase0 [9.62361e-07/1] Phase offset of best
fitting template
516- 537 E22.20 --- Phase1 [3.06546e-06/1] Phase offset of 2nd best
fitting template
539- 560 E22.20 --- Phase2 [3.93540e-06/0.999996] Phase offset of
3rd best fitting template
562- 583 E22.20 --- RSS0 [3.99068e-07/696961]? Residual Sum of
Squares (RSS) of best fit template
585- 606 E22.20 --- RSS1 [5.9748e-05/701646]? RSS of 2nd best fit
template
608- 629 E22.20 --- RSS2 [9.8591e-05/702625]? RSS of 3rd best fit
template
631- 652 E22.20 --- chi2-g [1.82028e-06/3.2428e+46]? Reduced chi
squared of light curve from constant
in DES g (4)
653 A1 --- f_chi2-g [I] I for infinity
655- 676 E22.20 --- chi2-r [2.14514e-06/1.45597e+51]? Reduced chi
squared of light curve from constant
in DES r (4)
678- 699 E22.20 --- chi2-i [5.13706e-07/373528]? Reduced chi squared
of light curve from constant in DES i
(4)
700 A1 --- f_chi2-i [I] I for infinity
702- 723 E22.20 --- chi2-z [1.52942e-06/545252]? Reduced chi squared
of light curve from constant in DES z
(4)
724 A1 --- f_chi2-z [I] I for infinity
726- 747 E22.20 --- chi2-Y [1.62728e-07/4.21637e+06]? Reduced chi
squared of light curve from constant
in DES Y (4)
749- 774 F26.20 --- Sig-g [0/20410.8]? Significance of light curve
in DES g (4)
776- 797 E22.20 --- Sig-r [0/18028.5]? Significance of light curve
in DES r (4)
799- 820 E22.20 --- Sig-i [0/30133.6]? Significance of light curve
in DES i (4)
822- 847 F26.20 --- Sig-z [0/23563.7]? Significance of light curve
in DES z (4)
849- 870 E22.20 --- Sig-Y [0/14540.5]? Significance of light curve
in DES Y (4)
872- 893 E22.20 --- RSS-dof-0 [3.99068e-07/9949.94]? RSS per degree of
freedom of best fitting template (3)
895- 916 E22.20 --- RSS-dof-1 [5.9748e-05/109327]? RSS per degree of
freedom of 2nd best fitting template
918- 939 E22.20 --- RSS-dof-2 [9.8591e-05/109651]? RSS per degree of
freedom of 3rd best fitting template
941- 963 E23.20 [-] Ichi-med [-2.93188/51.3637]? Median log(reduced
chi squared) across DES grizY (3)
965- 986 E22.20 --- RSS-Ichi-med [-999.467/9991.97]? (RSS/dof)/median
log(reduced chi squared) across DES
grizY (3)
988-1012 F25.20 --- Amp-RSS-0 [0.00011072/9970.12]? Best-fitting
amplitude divided by the best-fitting
RSS/dof (3)
1014-1038 F25.20 --- f-dist1-0 [0.000139949/1587.71] Distance of
Amplitude/Period for best fit template
(3) (5)
1040-1063 F24.20 --- f-dist1-1 [0.000131378/815.706]? Distance of
Amplitude/Period for 2nd best fit
template (5)
1065-1088 F24.20 --- f-dist1-2 [0.00011433/759.352]? Distance of
Amplitude/Period for 3rd best fit
template (5)
1090-1114 F25.20 --- f-dist2-0 [0.000181306/1587.71]? Distance of
Amplitude/Period for best fit template
(3) (6)
1116-1139 F24.20 --- f-dist2-1 [0.000175503/815.706]? Distance of
Amplitude/Period for 2nd best fit
template (6)
1141-1164 F24.20 --- f-dist2-2 [0.000101131/759.352]? Distance of
Amplitude/Period for 3rd best fit
template (6)
1166-1189 F24.19 --- kappa-0 [0.000564259/9972.2]? von Mises-Fisher
concentration parameter of phases for
best fitting template (3)
1191-1216 F26.20 --- kappa-1 [0.000306927/18264.3]? von Mises-Fisher
concentration parameter of phases for
2nd best fitting template
1218-1242 F25.19 --- kappa-2 [0.000383926/18628.4]? von Mises-Fisher
concentration parameter of phases for
3rd best fitting template
1244 I1 --- flag-minmax [0/3]? Flag for observations missing near
maximum and minimum light (7)
1246-1264 I19 --- Source Gaia DR2 source_id for cross-matched RRab
in Clementini et al. (2018,
J/A+A/622/A60) (0=not found in this
catalog)
1266 I1 --- PS1-RRab [0/1] Present in Sesar et al. (2017,
J/AJ/153/204) RRab catalog?
(0=No; 1=Yes)
1268-1280 I13 --- CSDR2-ID ID number from associated Catalina
Surveys DR2 RRab catalogs (0=not found
in this catalog)
1282-1298 A17 --- ATLAS-ID ID from Heinze et al. (2018,
J/AJ/156/241) ATLAS RRab catalog (0=not
found in this catalog)
1300-1306 I7 --- SDSS-ID [0/7913279] SDSS DR7 (Cat. II/294) ID
(0=not found in this catalog)
1308-1310 A3 --- SDSS-class Classification from SDSS stripe 82
studies from Sesar et al. (2010,
J/ApJ/708/717) or Ivezic et al. (2007,
J/AJ/134/973) (8)
1312-1341 A30 --- Simbad-ID Object identifier in SIMBAD database
(0=not found in this catalog)
1343-1355 A13 --- Simbad-class Object classification in SIMBAD database
(0=not found in this catalog)
1357-1376 A20 --- OGLE-ID OGLE ID from LMC and SMC RRAb catalogs
from Soszynski et al.
(2016AcA....66..131S 2016AcA....66..131S)
1378-1388 A11 --- CEMV-ID ID from Martinez-Vazquez et al. (2016,
J/MNRAS/462/4349) (0=not found in this
catalog)
1390-1395 I6 --- GCVS5-ID [0/820079] Cross matched ID with the
General Catalogue of Variable Stars v5.1
from Samus et al. (2017, Cat. B/gcvs)
(0=not found in this catalog)
1397-1401 A5 --- GCVS5-Type Variable type for cross matched object
(see file "vartype.txt" in the General
Catalogue of Variable Stars v5.1)
1403-1407 I5 --- hpx32 [5441/11819] Object's Healpix (nside=32)
used to subdivide the light curves
1409 I1 --- train [0/1] Identifies objects used to train
the Random Forest (0=not in training
set; 1=in training set)
1411 I1 --- rrab [0/1] Identified as a high confidence
RRab in this study (=1) or not (=0)
1413-1428 A16 --- ---
1429-1450 A22 --- File Filepath to the object's light curves
in subdirectory lc
1452-1465 A14 --- Com Comment from first author during visual
validation (9)
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Note (1): To convert to extinction in DES filters: Ag=3.6830*EBV,
Ar=2.6048*EBV, Ai=1.9401*EBV, Az=1.4505*EBV, AY=1.2774*EBV.
Note (2): Not corrected for Galactic dust extinction.
Note (3): Values used for Random Forest features.
Note (4): Values used for initial variability cuts.
Note (5): From Sesar et al. 2010, J/ApJ/708/717 Oosterhoff I relation.
Note (6): From Sesar et al. 2010, J/ApJ/708/717 curve separating the Oosterhoff
I and II groups.
Note (7): Flag as follows:
0 = At least 2 observations near maximum and minimum light;
1 = Fewer than 2 observations near minimum only;
2 = Fewer than 2 observations near maximum only;
3 = Fewer than 2 observations near both maximum and minimum light.
Note (8): Classification as follows:
ab = RRab;
c = RRc;
var = Variable;
std = Standard source;
0 = Not found in these catalogs.
Note (9): The possible comments and their meanings are as follows:
confirmed = Convincing RRab;
no_ = Rejected followed by a reason code;
maybe_ = Possible RRab followed by a reason code;
missing_image = Missing coadd image in SkyViewer.
Reason codes:
galaxy = DES image showed galaxy;
bad_fit = Poor template fit;
n_points = Few observations/poor phase coverage;
crowding = Object is very close to another object;
misc = Miscellaneous reasons;
0 = Not visually checked.
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History:
From electronic version of the journal
Table 11 and light curves downloaded from:
http://des.ncsa.illinois.edu/releases/other/y3-rrl (September 2019)
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 02-Sep-2019